Coated paper and process of producing same



Patented Fete. 6,. E934 Parent or ies coerce mere AND raocnss or rnonncrne sans .narles 1L. Gabriel, Lawrence, N. Y., assignorto (Commercial Haute, limit,

Solvents Corporation, a corporation of Maryland No Drawing. Application July 2,; 1931 Serial No. 548,482;

at Claims.

This invention relates to coated papers and a process of producing same.

In the past complicated and expensive methods of packing havebeen required of various articles 5 which may be subject to deterioration either by contact with a moisture or with the atmosphere itself, or on the other hand, by the lossof essential constituents of the article through evaporation. For example, the flavor and other desirable n properties of cigarettes, cigars, and other tobacco products are materially afiected by changes in the moisture content of the products. In order to maintain the moisture content of such products uniform, it has been customary to wrap them in tin foil, glassine, cellophane, and more recent still, in coated cellophane. Food products such as coffee gradually lose by evaporationappreciable proportions of their esential oil and flavor content unlem packed in metal or other suitable 2o containers which may be sealedso as to prevent a loss of these constituents. y From the point of view of the distributors the appearance of an article also has a very important bearing upon its marketability and for this reason the transparency of the wrapping material is most important. A wrapping material which in addition to being impervious to moisture and gases, is also transparent so as to allow inspection of the article to be sold, is particularly desirable for packages containing practically all varieties of food stulfs. Such wrapping materials are also very advantageously employed for protecting many other types of articles subject to easy soiling, as for example, stationery, clothing, etc.

The various types of wrapping materials previously available are subject to a great many disadvantages. Tin and lead foils are both relatively expensive and opaque and in addition, lead foil is 40 unsuitable for wrapping certain foodstufis due to its toxic properties. Ordinary cellophane is not only permeable to moisture and gases but is also fairly expensive. 7 Coated cellophane is moisture and gas proof but possesses the important dis- 4.5 advantage of being still more expensive than the uncoated grade of cellophane. Glassine is neither moisture proof nor very transparent. Pariffin coated paper is not completely transparent and in addition, possesses certain other important disadvantages. I

I have now discovered a new form of moisture proof transparent wrapping paper which possesses the desirable properties of the materials I just enumerated, with the important advantage of being much cheaper than any similar previously (Cl. ill-68) known material. My new paper may be produced by impregnating paper with compositions comprising cellulose esters and esters of the type resulting from the reaction of polybasic acids partly with dihydric alcohols'such as glycol and partly with a monohydric alcohol.

Esters of the type contemplated are represented by the formulae:

0.00.A.G0.0R

R\ and R 0.00.A.C0.0R OH where A represents the radicle of a polybasic acid, R the radicle of a polyhydric aclohol (glycol) and R the radicle of a monohydric alcohol.

Compounds of this type may be synthesized in a number of ways. For example, a polybasic acid may be mixed with proportionate quantities oi. glycol and a monohydrid alcohol, and the resulting mixture heated in the presence of an esterification catalyst. Preferably the glycol is first reacted with the polybasic acid and the product thus obtained reacted with a monohydric alcohol in the presence of an esterification catalyst. Still other methods may, of course, be employed if desired.

The following specific example will illustrate a method by which these compounds may be satisfactorily produced:

Example 150 grams of phthalic anhydride is heated with 30 grams of ethylene glycol. The temperature is raised to 180 C., after which the mixture is allowed to cool. 100 grams of normal butyl alcohol and 7 grams of sulphuric acid are then added, and the mixture is heated to distill oil the butyl alcohol and carries with it the Water formed during esterification. When about 30 c. c. of distillate has been cooled, 50 c.c. of fresh butyl alcohol is added and distillation is continued untilthe lower layer of condensate contains about 24 c. c. The product is washed with water, neutralized with sodium carbonate solution,

washed again and dried by heating in vacuo to 180 C. to remove low boiling impurities. The glycol butyl phthalate thus produced is a light yellow viscous oily mixture that can not be distilled without decomposition.

Other similar compounds which may be obtained by slight modification of the procedure set forth are glycol propyl phthalate, glycol benzyl phthalate, and similar esters of other polybasic acids such as terephthalic acid, tartaric acid,

citric acid. and the like. Other monohydric alcohols may also, of course, be substituted for those cited as examples. Examples of other suitable dihydric alcohols are: propylene glycol, butylene glycol, etc. Compounds of the type contemplated, therefore, may be designated as esters of the type resulting from the reaction of polybasic acids partly with dihydric alcohols such as glycol and partly with a monohydric alcohol, one or both of the hydroxyl radicles of the dihydric alcohol being combined with carboxyl groups of the acid, more than one molecule of which may be present in the ester.

In preparing my new coated paper I use a cellulose ester and an ester of the type hereinabove referred to, preferably incorporated in a suitable solvent and diluent so as to facilitate the coating or impregnation of the paper. The following examples will illustrate compositions of the character contemplated as suitable for coating papers:

Eaample I Per cent Cellulose nitrate 10-30 Glycol butyl phthalate 90-70 dissolved in a solvent mixture consisting of:

Per cent Ethyl acetate 40-50 Toluol 25-35 Ethanol 5-15 Butyl acetate 5-10 If desired a soluble dye of any particular color maybe incorporated in mixtures such as those cited above so as to give a colored paper.

The relative proportion of the constituents used in the examples cited above may, of course, be

varied considerably without departing from the scope of my invention. It is generally preferred, however, to use a fairly large excess of the said mixed ester as compared to cellulose ester. It is preferred also to use a solvent or solvent mixture which will evaporate and leave a dry film rather quickly. In case, however, forced drying or drying in an atmosphere of low humidity is not employed, the solvent mixture should be regulated so that the evaporation of the solvent will not be so rapid as to cause blushed or opaque films. This may generally be prevented by incorporating in the solvent mixture small amounts of high boiling solvents such as butyl acetate, diacetone alcohol, etc.

The composition comprising cellulose esters and glycol butyl phthalate or other similar mixed esters may be satisfactorily applied to the paper in a number of ways, and it may be applied to one or both sides of the paper, if desired. For example, long sheets of the paper to be coated may be passed through a bath containing the cellulose ester-glycol butyl phthalate solution and thence preferably between rolls or scrapers to remove the excess solution. The sheet is then pref erably passed through a heated tunnel where the solvents are expelled from the sheet, leaving it coated or impregnated with the cellulose esterglycol butyl phthalate composition. When dried the coated sheet may be rolled, folded, or otherwise disposed of. The expelled solvents may be recovered, if desired, by the usual solvent rem ry methods.

The thickness of the film applied to the paper may be regulated by varying the quantity of the solvent, the proportion of cellulose ester to glycol butyl phthalate or other similar mixed esters, the grade (viscosity) of cellulose ester, the distance of the rollsor scrapers from the paper, etc. For most purposes, a coating approximately 0.0015 inches thick gives very satisfactory results.

The coated sheets produced as hereinabove disclosed are substantially impervious to moisture and gases, possess a satisfactory degree of flexibility and are not appreciably affected by greasy ormoist articles with which they come in contact. They also possess the advantage of being substantially transparent when a paper such as tissue paper, glassine, or other thin paper is employed as the material to be coated. They are also much cheaper to manufacture than other transparent moisture proof wrapping papers of similar character. Now having disclosed my invention, what I desire to claim is:

1. As a new article of manufacture, a papertreated with a composition containing a cellulose ester, the major non-volatile constituent of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

2. As a new article of manufacture, a paper treated with a composition containing nitrocellu lose, the major non-volatile constituent of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

3. As a new article of manufacture, a paper treated with a composition containing nitrocellulose, the major non-volatile constituent of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol, both of the hydroxyl groups of the dihydric alcohol being combined with carboxyl groups of the acid.

4. As a new article of manufacture, a paper treated with a composition containing nitrocellulose, the major non-volatile constituent of said composition consisting of an ester resulting from the esterification of a polybasic aromatic acid, partly with a glycol, and partly with an aliphatic mono-hydric alcohol.

5. As a new article of'manufacture, a paper treated with a composition containing nitrocellulose, the major non-volatile constituent of said composition consisting of glycol butyl phthalate.

6. As a new article of manufacture, a paper treated with a composition containing a cellulose ester, from 70-90% of the non-volatile constituents of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

-'7. As a new article of manufacture, a paper treated with a composition containing nitrocellulose, from 70-90% of the non-volatile constituents of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

8. As a new article of manufacture, a paper treated with a composition containing nitrocellu lose, from 70-90% of the non-volatile constituents of said composition consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol, both of the hydroxyl groups of the dihydric alcohol being combined with carboxyl groups of the acid.

9'. As a new article 0t manufacture, a paper treated with a composition containing nitrocellulose, from 70-90% of the non-volatile constituents of said composition consisting of an ester resulting from the esterification of a polybasic aromatic acid, partly with a glycol, and partly with an aliphatic mono-hydric alcohol.

10. As a new article of manufacture, a paper treated with a composition containing nitrocelluthe dihydric alcohol being combined with carboxyl' lose, from 70-90%-of the non-Volatile constituents of said composition consisting of glycol butyl phthalate.

11. A process for producing coated paper which comprises applying to paper a solution containing a cellulose ester, the major non-volatile constituent of said solution consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

' 12. A process for producing coated paper which comprises applying to paper a solution containing nitrocellulose, the major non-volatile constituent of said solution consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a monoof said solution consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a monohydric alcohol, both of the hydroxyl groups of groups of the acid.

14. A process for producing coated paper which comprises applying to paper a solution containing nitrocellulose, the major non-volatile constituent of said solution consisting of an ester resulting from the esterification of a polybasic aromatic acid, partly with a glycol, and partly with an aliphatic mono-hydric alcohol.

15. A process for producing coated paper which comprises applying to paper a solution containing nitrocellulose, the major non-volatile constituent of said solution consisting of glycol butyl phthalate. I

16. A process for producing coated paper which comprises applying to paper a solution containing a cellulose ester, from 70 90% of the non-volatile constituents .of said solution consisting of an ester resulting fromthe esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a mono-hydric alcohol.

17. A process for producing coated paper which comprises applying to paper a solution containing nitrocellulose, from 70-90% of thenon-volatile constituents of said solution consisting of an ester resulting from the esterification of a polybasic acid, partly with a dihydric alcohol, and partly with a inon'o-hydric alcohol.

18. A process for producing coated paper which with a mono-hydric alcohol, both of the hydroxyl groups of the dihydric alcohol being combined with carboxyl-groups of the acid.

19. A process for producing coated paper which comprises applying to paper a solution containing nitrocellulose, from 70 90% of the non-volatile constituents of said solution consisting of an ester resulting from the esterification of a polybasic aromatic acid, partly with a glycol, and partly with an aliphatic monoahydric alcohol.

20. A process for producing coated paper which- -comprises applying to paper. a solution containing nitrocellulose, from 70-90% of the non-volatile constituents of said solution consisting of gly- 'col butyl phthalate.

CHARLES L. GABRIEL. 

